In the field of radiopharmaceutical synthesis, automated synthesizers are employed to operate within the confines of a hot cell to perform the steps of synthesizing and dispensing a radiopharmaceutical. Space within a hot cell is generally at a premium as for each synthesizer a hot cell must as well accommodate ancillary equipment to the synthesizer, such as an HPLC injector and column, dispense vials, waste vessels, reagent vessels, and connective tubing associated with each synthesizer. Between synthesis runs on a synthesizer, an operator typically needs access to the hot cell to, eg, swap out synthesis cassettes used with the synthesizer, check connections to or from the synthesizer or cassette, etc. The waste vessel associated with the synthesis run can contain a significant proportion of the activity that originally came from the cyclotron, as much as 60% of that starting activity. When the operator must empty the waste container between runs, wait times will be increased for radioisotopes having a longer half-life, e.g., 18-F which has a 2-hour half-life. Thus, the waste vessels provided within the hot cell may contain a source of significant radioactive hazard to the operator. While the waste vessel may be shielded, such shielding takes up additional space within the hot cell. Additionally, it is almost always specified that the waste vessel be emptied at the beginning of each run for a drug product, because the impact of the presence of the waste on the subsequent run cannot be determined with complete certainty. Thus a subsequent synthesis run can experience a catastrophic failure due to the presence of the waste from a previous run remaining in the waste vessel for the subsequent run.
Systems have been developed for drawing the contents of the waste vessel into a secondary waste vessel, possibly even outside the hot cell in a shielded enclosure, to reduce operator exposure to the activity of the waste fluid. Some previous attempts to provide systems for emptying a waste vessel containing radioactive waste fluid include providing a positive pressure to a container through an inlet port so as to direct the fluid through and outlet port. Systems providing a positive motive pressure to a radioactive fluid run risks of over-stressing the fittings and junctures along the path of fluid flow. Additionally, some synthesis systems may actively limit the pressure that may be imposed on a waste vessel by countering the pumping of additional pressuring gas by applying a vacuum to the waste vessel should the pressure within the waste vessel exceed a pre-set limit.
Other attempts have provided a negative pressure (ie, a low pressure) at the outlet port so as to draw the fluid through the outlet port. See, eg, commonly-assigned WO 2012/092564. These systems providing negative pressure to the waste vessel have provided an active pump for applying the negative pressure through a secondary waste vessel to the primary waste vessel as the motive force for the fluid transfer, thus requiring careful control of the negative pressure pump so as not to overdraw the waste fluid beyond the secondary waste vessel.
The art thus lacks a system and method for utilizing a negative pressure motive force without the need for an active negative pressure pump during the fluid transfer.